[PATCH v6 5/5] kunit: Add documentation for warning backtrace suppression API

Albert Esteve
2026-03-17T09:25:43Z

From: Guenter Roeck <linux@roeck-us.net>

Document API functions for suppressing warning backtraces.

Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
Documentation/dev-tools/kunit/usage.rst | 30 +++++++++++++++++++++++++++++-
1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index ebd06f5ea4550..f1f8e2619d2d6 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -157,6 +157,34 @@ Alternatively, one can take full control over the error message by using
if (some_setup_function())
KUNIT_FAIL(test, "Failed to setup thing for testing");

+Suppressing warning backtraces
+------------------------------
+
+Some unit tests trigger warning backtraces either intentionally or as side
+effect. Such backtraces are normally undesirable since they distract from
+the actual test and may result in the impression that there is a problem.
+
+Such backtraces can be suppressed. To suppress a backtrace in some_function(),
+use the following code.
+
+.. code-block:: c
+
+ static void some_test(struct kunit *test)
+ {
+ DEFINE_SUPPRESSED_WARNING(some_function);
+
+ KUNIT_START_SUPPRESSED_WARNING(some_function);
+ trigger_backtrace();
+ KUNIT_END_SUPPRESSED_WARNING(some_function);
+ }
+
+SUPPRESSED_WARNING_COUNT() returns the number of suppressed backtraces. If the
+suppressed backtrace was triggered on purpose, this can be used to check if
+the backtrace was actually triggered.
+
+.. code-block:: c
+
+ KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(some_function), 1);

Test Suites
~~~~~~~~~~~
@@ -1211,4 +1239,4 @@ For example:
dev_managed_string = devm_kstrdup(fake_device, "Hello, World!");

// Everything is cleaned up automatically when the test ends.
- }
\ No newline at end of file
+ }

--
2.52.0